Communication systems on which data messages are transmitted are well known in the art. Before a user may transmit data, many systems require a data communication unit to first request a communication resource, such as a wireline, frequency, frequency pair, TDM (time division multiplexed) time slot, a recurring TDMA (time division multiple access) time slot, a single-shot use of a sequence of TDMA time slots, and so forth. By way of a controller or other resource allocation device, the system receives the request, also known as a reservation request, allocates a communication resource, and transmits a reservation grant that provides the user of the data unit with the exclusive use of the assigned communication resource during an allotted time. In systems supporting voice communications, communication resources may be allocated in basically the same manner.
Communication systems also provide control channels that comprise communication resources reserved for communications between member communication units and the communication infrastructure for the purposes of, inter alia, transmitting reservation requests and reservation grants to gain/grant system access. Most control channels in dispatch communication systems and other trunked communication systems are half-duplex in nature. An example of a full-duplex control channel can be found in U.S. Pat. No. 5,574,788, wherein a full-duplex control channel allows for "simultaneous in-bound and out-bound signalling" of control information. Such an approach, however, is far from desirable. It is quite costly to implement, often leads to a waste of valuable bandwidth, and will typically lead to wasteful battery consumption in a portable unit. Further, there is no particular value to the average user that might offset these significant costs.
In communication systems today, it is possible for both voice communications and data communications to be assigned to the same communication resource. TDMA, a common method for allocating communication resources, breaks the channel into individually allocatable time slots. Voice and circuit data communications typically take place in a recurring reserved TDMA time slot, whereas packet data communications typically take place in a single-shot use of a sequence of TDMA time slots. Both voice communications and data communications in a communication system may be full-duplex communications, wherein a single communication unit transmits and receives at the same time. Both voice communications and data communications in a communication system may be half-duplex communications, wherein a communication unit at any given time may only transmit or receive on a communication resource, but may not do both. Some communication units, although full-duplex, may need to only transmit or receive during a given period of time. In addition, all communications allocated to a particular full-duplex communication resource(s) may be reserved as full-duplex communications, even though the communication unit is not capable of full-duplex communications.
A single communication system may handle both voice and data communications, as well as both full-duplex and half-duplex communications. As a result, when a system controller allocates communication resources to support reservation requests, a communication system with both full-duplex and half-duplex communication units may have a communication resource allocated to these various communications as shown in FIG. 1. In the timing diagram of FIG. 1, inbound transmissions and outbound transmissions are shown for the same communication resource. Full-duplex communications 101 and 107 occupy both the inbound and outbound bandwidth of the communication resource depicted. Inbound only transmissions 103 and 111 and outbound only transmissions 105, 109, and 113 are shown in the appropriate inbound and outbound portions for the communication resource. As can be seen from the timing diagram of FIG. 1, much valuable bandwidth for the depicted communication resource is wasted because some communications 103, 105, 109, 111, and 113 occupy only one-half of the allotted bandwidth, either inbound or outbound, whether the transmission is sourced by full-duplex or half-duplex communication units.
Accordingly, there is a need for a method of allocating communication resources, which method efficiently allocates inbound and outbound resources without wasting valuable bandwidth.